Page 99 holds up pretty well to the test. There are two main themes in this book, both attempting to explain why Neanderthals went extinct. The first theme is that modern humans are an invasive species and, in fact, an invasive predatory species. In order to understand what this means, I often use the results of studies arising from the reintroduction of gray wolves to the Greater Yellowstone Ecosystem in 1995-6. That is the major topic of page 99, which discusses the effects of the return of wolves to Yellowstone, where they had been absent since about 1920, thanks to the killing propensities of humans. Thus, the “normal” ecosystem that had reigned in Yellowstone for many decades was in fact depauperate. When wolves came back, their closest competitor – coyotes – suffered. Wolves targeted coyotes for hunting and, as coyotes tried to scavenge from wolf kills, wolves killed them. Coyote populations dropped by 50 percent overall and those remaining started avoiding wolf-rich areas.

The analogy to modern humans invading Eurasia and meeting Neanderthals suggests that Neanderthals, as the indigenous predator closest to modern humans, would suffer the most precipitate drop in population and the most severe competition from the human invasion.

Where page 99 fails to capture the main point of the book is in terms of the second theme, how modern humans outcompeted Neanderthals. Later in the book I argue that there is good evidence for the existence of a unique group of large canids which I call wolf-dogs. It has been suggested that these animals were a first attempt at domesticating wolves into dogs. The second theme of the book explores evidence for these wolf-dogs – morphological, genetic, and dietary – and what having even partly domesticated wolf-dogs might have meant to hunting success among modern humans. I shape and present a novel – and controversial – hypothesis that these animals were wolf-dogs and worked with humans to explain their unprecedented success in hunting.

Only time and more evidence will reveal whether this domesticated dog hypothesis is correct, but the ideas in the book are new and thought-provoking.